The optimization of engine parameters, best nozzle hole and piston bowl geometry is highly marked for bio-fuel operation as they have slightly higher viscosity and lesser heating value than the petroleum diesel. In the first phase of work, at single fuel operation, study optimized the best fuel blend as B20 (among B10, B20, B30 and B100), injector opening pressure as 230 bar (among 210, 220, 230 and 240 bar), injection timing as 26. deg.bTDC (among 20, 23, 26 and 29. deg.bTDC), nozzle as 5 holes (among 3, 4 and 5 holes) and piston bowl geometry as re-entrant toroidal piston bowl geometry (among Hemispherical piston bowl geometry (HPBG), Straight sided piston bowl geometry (SSPBG), Toroidal piston bowl geometry (TPBG) and Re-entrant toroidal piston bowl geometry (RTPBG)). Hence, baseline engine is modified with all these optimized parameters and then modified engine is carried further for dual fuel experiments. In second phase of the work, study unfolds the effect of injection timing (IT) on dual fuelled (B20+Bio-CNG (enriched methane)) modified engine. From the dual fuelled engine study, it is revealed that 29. deg.bTDC IT has shown the improved performance, combustion and emission characteristics when compared to 20, 23, 26 and 32. deg.bTDC injection timings. (C) 2019 Elsevier Ltd. All rights reserved.